JPH02272092A - Ferroelectric liquid crystal composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a novel liquid crystal composition useful as an electro-optical display material, and in particular provides a liquid crystal material having ferroelectricity, which is different from conventional liquid crystal compositions. The object of the present invention is to provide a liquid crystal material that has particularly excellent responsiveness and memory performance compared to liquid crystal materials, and can be used for liquid crystal display elements.

[Prior art]

The currently widely used liquid crystal display elements are mainly of the TN type, which utilizes nematic liquid crystals, and although they have many advantages, their responsiveness is inferior to that of light-emitting types such as CRTs. Compared to the display method, it had the major drawback of being much slower. Although many liquid crystal display systems other than the TN type are being considered, 1. Improvements in its responsiveness have not been readily achieved.

However, in liquid crystal devices using ferroelectric smectic liquid crystals, the 100 to 10
It has recently been revealed that because it is capable of a 00 times faster response and has bistability, it can retain the display even when the power is turned off (memory effect). For this reason, it has great potential to be used in optical shutters, printer heads, flat-screen televisions, etc., and research and development is currently being conducted in various fields to put it into practical use.

The liquid crystal phase of the ferroelectric liquid crystal belongs to the tilted chiral smectic phase, and among these, the one that is practically desirable is the chiral smectic C (hereinafter abbreviated as S01) phase, which has the lowest viscosity. It is called.

[Problem to be solved by the invention]

Liquid crystal compounds exhibiting the S01 phase (hereinafter referred to as SC''' compounds) have been studied and many compounds have already been synthesized.
c" compound alone must meet the following conditions for use as an optical switching element for ferroelectric liquid crystal displays: (a) exhibiting ferroelectricity in a wide temperature range including room temperature; and (b) exhibiting appropriate properties in a high temperature range. Having a phase series (c) Particularly chiral nematic (hereinafter abbreviated as N).

) exhibiting a long helical pitch in the phase; (d) having an appropriate tilt angle; (e) having low viscosity; (f) exhibiting a large spontaneous polarization above a certain level. No material has been known that satisfies all of (1), (5), (e), and (f), which include good orientation as a result of (1), and high-speed response as a result of (f).

Therefore, at present, liquid crystal compositions exhibiting the SCI phase (hereinafter referred to as S01 liquid crystal compositions) are currently being used for studies and the like.

In order to obtain good orientation, for example, JP-A-61-1
As shown in Japanese Patent No. 53623, etc., in a liquid crystal having an N1 phase in the high temperature range of the "sc" phase, it is generally effective to increase the length of the helical pitch of the N* phase.In this case, The orientation is better when the smectic A (hereinafter abbreviated as SA) phase is present in the temperature range between the S01 phase and the N0 phase, and in order to increase the helical pitch, an optically active substance that causes left helix and an optically active substance that causes left helix are used. It is also known that it is possible to use a combination of optically active compounds that produce a right-handed helix (nematic (hereinafter abbreviated as N)). (It is already a known technique to adjust the orientation.) However, although these techniques can provide good orientation, they do not necessarily provide high-speed response.

In order to exhibit high-speed responsiveness, low-viscosity smectic C (hereinafter abbreviated as SC) is used, for example, as shown in the special lecture at the 12th Liquid Crystal Conference (Proceedings of the same conference P, 9B). ) phase (hereinafter referred to as SC matrix liquid crystal) has a spontaneous polarization (hereinafter abbreviated as Ps).

) is better.

According to this method, the proportion of the optically active compound that produces a helix is reduced, so the helical pitch becomes relatively long. need to be,
As a result, the spontaneous polarization became too small, resulting in a problem that high-speed response could not be obtained.

Further, those that have been used hitherto as SC matrix liquid crystals are described in, for example, Japan Display '86 Lecture Proceedings (from page 352) or Japanese Patent Application Laid-Open No. 1983-583.

RO+COO+OR' (R, R' represent an achiral alkyl group) (R,
R' is the same as above. ), the compound itself or its homologues are limited to those exhibiting an SC phase, or compositions in which a liquid crystal compound is added that exhibits a strong dipole (polarization) in the direction perpendicular to the long axis of the molecule. However, if the temperature range of the SC phase is kept wide, the viscosity increases, and if the viscosity is decreased, the temperature range of the SC phase becomes narrow.

Therefore, with the prior art, it has been difficult to simultaneously achieve good orientation and high-speed response.

The problem to be solved by the present invention is to provide a ferroelectric liquid crystal composition that is fully satisfactory in both high-speed response and orientation.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a liquid crystal composition (
A ferroelectric liquid crystal composition comprising a chiral dopant consisting of an optically active compound added to SC matrix liquid crystal (hereinafter referred to as SC matrix liquid crystal used in the present invention), in particular, the viscosity-reducing liquid crystal is represented by the following general formula (A). A ferroelectric liquid crystal composition containing at least one of the compounds shown above and exhibiting an S01 phase in a wide temperature range including room temperature is provided.

(In the formula, R1 and Rh each independently have 1 to 1 carbon atoms.
18 straight-chain or branched alkyl group, R1
At least one of R and R represents a linear alkyl group. R''' and Rb each independently have 4 to 4 carbon atoms;
A linear alkyl combination of 12 is particularly preferred.

The SC base liquid crystal used in the present invention has a phase sequence of (a) I (isotropic liquid) phase → N phase → SA phase → SC phase on the high temperature side of its SC phase when the temperature is lowered (b) ! A phase sequence that has a phase sequence of phase → SA phase → SC phase (c) a phase sequence of ■ phase → N phase → SC phase, or (d) a phase sequence of I phase → SC phase However, the selection of (a) to (d) differs depending on the chiral dopant used at the same time. The most commonly used method is (a), which shows the nematic property of the chiral dopant (when added to the SC matrix liquid crystal, N
If the smectic A property of the chiral dopant (tendency to widen the temperature range of the 0 phase and narrow the temperature range of the SA phase) is strong,
If there is a strong tendency to widen the temperature range of the A phase and narrow the temperature range of the N0 phase, select (c), or if the SC property is weak and the temperature range of the N9 or SA phases tends to be widened. It is most suitable to use (d) 0 What is important is the phase series when using S00 liquid crystal composition, - For boat fishing, the phase series of ■→N"→SA→SC1 On the other hand, the phase series ■→N1→S01 may also show better orientation depending on the orientation control method.
Also, since it is easy to obtain a large tilt angle, it is suitable for guest-host systems.

As the SC base liquid crystal used in the present invention, a composition consisting of a compound exhibiting an SC phase as conventionally used can be used, but in order to obtain faster response, the composition shown below can be used. is more preferable.

That is, (I) a composition (hereinafter referred to as medium-temperature liquid crystal) consisting of a compound that has a two-ring structure and exhibits an SC phase at a temperature close to room temperature, or a homolog thereof (a compound that differs only in the alkyl chain);
(■) A composition with a two-ring structure, few polar groups in the molecule, and a low viscosity compound (hereinafter referred to as viscosity-reducing liquid crystal) to lower the viscosity and improve responsiveness.

(1) Medium-temperature liquid crystal The medium-temperature liquid crystal used in the present invention is such that the liquid crystal compound constituting it is optically inactive, has a two-ring structure, and has an S
A compound exhibiting C phase or the number of carbon atoms in its alkyl chain,
It consists of homologues that differ only in shape, and at least one compound among the homologs has a
It is a compound that exhibits an SC phase that may be monotropic in the temperature range of C6 or higher.

Typical compounds used as medium-temperature liquid crystals are listed below. However, in the general formula shown below, R+
, Rt each independently represents an alkyl group having 1 to 18 carbon atoms.

([-a) (T-a-46) (1-a-47) (1-a-48) (1-a-49) (1-a-50) (1-a-51) (1-a-52) (1-a-53) R, ritoocOR.

R+Gobashi C0OR.

=4. q arc 0 COR.

RtO 慟恰C00R1 R, C00 ('9th printing>R.

R, COO Jinkatsu 0R2 RICOO Haruka Hshi0CORz R,C(to)zu>C0ORχ (1-b) (1-c) (I-c-29) (1-c-30) R, OCO÷coo surface OR.

-N R moxibustion coo+R2 (1-c-32) R,C00((叉coo佽R2 (1-c-34) R10(i005 amount R2 (1-c-36) RICOO+COO zutsu2 (1- d) Among the above compounds, formula (1
-a) and the compound represented by the formula (1-b) are preferred, and the compounds represented by the formula (1-a-1), the formula (1-a-2), and the formula (1-a-
5), formula (1-a-6), formula (1-a-41), formula (1
-a-42) and compounds represented by formula (1-b-1) are particularly preferred.

(I [) Reduced viscosity liquid crystal The reduced viscosity liquid crystal used in the present invention is a low-viscosity liquid crystal compound or composition, and the constituent low-viscosity compound has a two-ring structure, and the carbon atoms of the alkyl chains in both chains are Homologues that differ only in the number of atoms and their shapes do not show the SC phase, but
By adding it to a medium-temperature range base liquid crystal, it contributes to improving responsiveness, and at least one of both chains is an alkyl group, particularly preferably a compound in which both chains are an alkyl group. The ester bond contained in is 1
less than or equal to

The present invention is particularly characterized by containing a compound represented by the above general formula (A) as a viscosity-reducing liquid crystal.

-i Representative compounds represented by formula (A) and their phase transition temperatures are listed in Tables 1 to 4.

Table 1 (Continued) In the upper table, Cr represents a crystalline phase, SA represents a smectic A phase, N represents a nematic phase, and ■ represents an isotropic liquid phase.

・ indicates that the phase exists, - indicates that the phase does not exist (or cannot be confirmed), and the number to the right of ・ indicates the transition temperature from that phase to a phase in a higher temperature range. indicates that the phase is monotropic.

All of these compounds show N phase or SA phase, but SC
Phases are not shown. Generally, when a liquid crystal compound exhibiting such a phase transition is added to a liquid crystal composition exhibiting an SC phase, its Tc
(the upper limit temperature of the SC phase) is often significantly lowered. However, when the compound of formula (A) of the present invention is added, the Tc decrease is small, and the viscosity of the liquid crystal composition exhibiting the SC phase is reduced, making it possible to greatly improve the response.

As the viscosity-reducing liquid crystal, a compound represented by the general formula (D) shown below can also be used in combination with a compound represented by the general formula (A).

Rj Q V-C←R angle...(D) R1 and R
'' each independently represents a linear or branched alkyl group or alkoxyl group having 1 to 18 carbon atoms, at least one of which represents an alkyl group, preferably 3 carbon atoms.
~12 represents a linear alkyl group, and ■ is -COOOOCOC1l! O0CHz-GHzGHz
, Q=(: , COS , 5CO
- or represents a single bond.

The blending ratio of the medium temperature range liquid crystal is preferably 10 to 99% by weight, particularly preferably 60 to 95% by weight, based on the SC base liquid crystal. The blending ratio of the viscosity-reducing liquid crystal is preferably 1 to 90% by weight, particularly preferably 5 to 40% by weight, based on the SC base liquid crystal.

It is preferable that the reduced viscosity liquid crystal contains the compound represented by the above general formula (A) in an amount of 20% by weight or more, particularly 40% by weight or more.

The chiral dopants used in the present invention include (1)
(2) a compound that exhibits only a liquid crystal phase other than the SC'' phase, or (3) a compound that does not exhibit any liquid crystallinity, but in the case of (3), S
In order to prevent the tendency for the liquid crystallinity of the SC* liquid crystal composition obtained by adding it to the C matrix liquid crystal to decrease, it is preferable to use a compound having a skeleton similar to that of a liquid crystal.

Among the various physical properties that a chiral dopant brings to an SC* liquid crystal composition, the important ones are the helical pitch it induces, the direction and magnitude of spontaneous polarization, and these are dependent on the optically active site of each compound constituting the chiral dopant. most affected by

Typical optically active groups in optically active compounds that have been used as chiral dopants, SC" compounds, or additives to nematic liquid crystals are listed below.

<IV-32) CH3 -O-C1l-R4 (IV-53) C11゜CIl OR5 0 C1l! C)l R5 0 C1 COC1h CHRs ([V-57) -O-CIl□-CH-R5 吋-COOCH□-Cll Rs (IV-71) CH,3 -O-C1l-C1+, -0-COR6( IV-75) C1h OC)12 CIl 0Rs (IV-76) C11゜-5-C8-ps (IV-78) Cl+15 0 C1(2CIl 0R6 CI+3 (■-82) N Cl1 Rs In each of the above general formulas, m represents an integer from 1 to 4, and n
represents an integer of 1 to 10, R3 represents an alkyl group having 3 to 8 carbon atoms, R4 represents an alkyl group having 2 to 10 carbon atoms, and R3 represents an alkyl group having 1 to 10 carbon atoms. , R6 represents an alkyl group having 1 to 4 carbon atoms.

In optically active compounds containing only optically active groups represented by formulas (IV-1) to (rV-22), when added to an SC base liquid crystal to form an SC''' liquid crystal composition, The spontaneous polarization caused by SC is often small, and SC
Even if it shows two phases, most of them are 1Onc/cfl”
No more than the following.

On the other hand, as optically active groups, formulas (IV-31) to (■-9
Many of the optically active compounds containing the optically active group represented by 1) induce a large spontaneous polarization when added to an SC matrix liquid crystal to form an "sc" liquid crystal composition;
In some cases, such as when exhibiting a phase, a large value of 300 nC/cm'' or more exists.

Typical basic skeletons of optically active compounds having such an optically active group at the end are listed below.

(V-12) 10ΣCH! O non) 0 mountain 100 Σ (V-60) public - [stock] (V-84) -Qbe) ... -'s (V-108) ◇) oco -○be now (V-132) minute oco-/': Imabohei (V-156) Min0CIIχ-〇(V-180) Sho (he) relative0CH2÷ (V-204) Ri+oco〈Hane (V-228) Stone Xφ) oco→shi( V-253) 0 day DCllzO□□□- (V-500) and +COOpe^ Fluorine atom, chlorine atom, bromine atom, methyl group, methoxy group, cyano group or Each basic skeleton substituted with 21.4 groups can also be used.

/ The optically active compound having the chiral group bonded to one or both sides of the basic skeleton as described above can be effectively used as a constituent component of a chiral dopant. In particular, general formula (B) in which the above chiral groups are bonded to both sides Ql-Z Ql [wherein, Q" and Q" are mutually different optically active groups, and each optically active group has at least one asymmetric At least one of Ql1'' and Ql1 has a carbon atom, and the asymmetric carbon atom is directly bonded to oxygen, iodine, nitrogen, fluorine, chlorine, or -C- or -C=N. Z represents a structure in which any one or two hydrogen atoms on these rings are substituted with a fluorine atom or a cyano group; In , Yl and Yt each independently represent a single bond, -COO--oc
o--co□O,'0(Jlz CHzCII□
--c = ic --cos- or -5CO-, but a single bond, Coo OCOCFIto- or -OCO. - is preferable, and in the case of m-1, it is preferable that at least one of YI and Yt is a single bond. ) represents the central skeleton (core) portion of a liquid crystal molecule represented by the following. Optically active compounds represented by the following are preferable.

-1ife In the optically active compound represented by formula (B), in particular, at least one optically active group is the (rV-
31) to (IV-91) are preferable.

As described above, the following points can be cited as advantages of using an optically active compound in which different chiral groups are bonded to both sides of the basic skeleton.

(1) It can exhibit stronger spontaneous polarization than a compound having a chiral group on only one side.

That is, a chiral group selected from the groups represented by (IV-31) to (IV-91) and (IV-1) to (IV-2)
2) A compound having chiral groups selected from the groups represented by (IV-31) to (■-91) on both sides of the basic skeleton, and a compound having the same basic skeleton with chiral groups selected from the groups represented by (IV-31) to (■-91). Compounds with only one group and an achiral group on the other side are added to the SC base liquid crystal, and when the spontaneous polarization is determined as an extrapolated value, it is found that the compound having chiral groups on both sides has a 10 to 30r+C /cmz or larger. The spontaneous polarization derived from the groups represented by (IV-1) to (IV-22) is at most 10 nC/cya.
It can be seen that it is thicker than the simple sum of the spontaneous polarizations due to the chiral groups on both sides.

Furthermore, in a compound that is a group selected from the groups represented by (fV-31) to (IV-91) and has different chiral groups on both sides of the basic skeleton, the spontaneous polarization due to both chiral groups is Polar ((S)-2-ethylbutyl b-decyloxybenzylidene aminophenyl cinnamate (DOBAMBC), a well-known ferroelectric liquid crystal)
The polarity of is determined as e. ), a very large spontaneous polarization can be obtained.

In this case, a larger spontaneous polarization of 100 nC/cm'' or more can be obtained than the simple sum of the spontaneous polarizations due to the chiral groups on both sides.

As a chiral dopant, the larger the spontaneous polarization it induces, the less it needs to be used.
The proportion of C matrix liquid crystal can be increased, and as a result, S
It is possible to reduce the viscosity of the CI liquid crystal composition. as a result,
This leads to improved responsiveness.

(2) It is possible to adjust the helical pitch, such as a compound with a very long helical pitch or a very short helical pitch induced in the NI phase or SC1 phase.

As mentioned above, in order to obtain good orientation, the N′″
It is important that the helical pitch in the phase or S04 phase is long. It is only necessary that the helical pitch of the chiral dopant is adjusted as a whole, and this is not necessarily necessary for each individual compound, but it is easier to adjust the helical pitch if the main component of the chiral dopant has a somewhat longer helical pitch. It is. Further, in the case of a compound added primarily for the purpose of adjusting the helical pitch, the shorter the helical pitch, the more convenient the amount added can be suppressed.

In order to lengthen the helical pitch, the directions of the helical pitch due to the chiral groups on both sides should be opposite to each other, but (IV-31
) to (IV-91), it is preferable that the polarities of their spontaneous polarizations be the same.

(3) Particularly (IV-31) ~ which can show large spontaneous polarization
Chiral groups selected from the groups represented by (IV-91) obtained by chemical methods such as asymmetric synthesis and optical resolution often do not have 100% optical purity; It is quite difficult to purify these to 100%. However, (S) obtained from natural products
-When combined with a chiral group derived from 2-methylbutanol or a chiral group with extremely high optical purity such as those obtained by microbial engineering techniques, these become diastereomers, which can be easily separated by chromatography or recrystallization. Therefore, the optical purity can be brought close to 100%.

It is effective to use the compound of general formula (B) in an amount of 10% or more, preferably 30% or more, particularly preferably 50% or more as a constituent component of the chiral dopant.

Among the compounds of general formula (B), compounds having particularly preferable combinations of basic skeleton and chiral group are shown below.

In the above general formula, R4 and R4r each independently represent an alkyl group having 2 to 10 carbon atoms, R5, R, and r each independently represent an alkyl group having 1 to 10 carbon atoms,
R1 is a linear alkyl group having 2 to 10 carbon atoms, a branched alkyl group having 3 to 10 carbon atoms, or an optically active group containing at least one asymmetric carbon having 4 to 10 carbon atoms. represents an alkyl group, i represents an integer of 0 to 5,
Y is a single bond, -o-, -oco-, -coo-, or -
ocoo -, W is chlorine fluorine or -〇-C
represents H3, and Z' is.

XI and X4 each independently represent a hydrogen atom, a fluorine atom or a cyano group, X2 represents a hydrogen atom or XI,
X3 represents a hydrogen atom or X4 COO- 0CO- -CI+! 0--OCII□-1 or at least one of X4 represents a hydrogen atom.

The above chiral dopant is present in the SC matrix liquid crystal at 1 to 60%.
It is appropriate to add it in a proportion of 2% by weight and use it as an S01 liquid crystal composition, but it is more preferable to add it in a proportion of 2 to 50% by weight. When the addition ratio of the chiral dopant is more than 60% by weight, the spontaneous polarization increases, but since the chiral dopant itself has a much higher viscosity than the base liquid crystal, the viscosity of the SCI liquid crystal composition increases, resulting in high speed This is undesirable because it tends to have an adverse effect on the response.Increasing the amount of chiral dopant added is also undesirable because it tends to shorten the helical pitch and adversely affect the orientation. If the addition ratio is less than 1% by weight, the spontaneous polarization will be too small and high-speed response cannot be expected.

The spontaneous polarization value of the S01 liquid crystal composition is 3 to 30 nC/c
It is preferable to adjust the addition ratio of the chiral dopant so that it is within the range of 100 nC/am, and in the case of a chiral dopant exhibiting an SC* phase, it alone exhibits a spontaneous polarization of about 100 nC/am, or an intensity equivalent to that. In the case of a chiral dopant that induces spontaneous polarization, the addition ratio of the chiral dopant is preferably in the range of 10 to 40% by weight, and 300nC/
In the case of a chiral dopant that exhibits a strong spontaneous polarization of cm" or more, the addition ratio of the chiral dopant is preferably in the range of 2 to 25% by weight. The stronger the spontaneous polarization induced by the chiral dopant, the more the most desirable addition ratio decreases. However, in the chiral dopants made of the optically active compounds exemplified, the addition ratio is never less than 1% by weight.

When the S01 liquid crystal composition of the present invention is cooled from an isotropic liquid state, it undergoes a phase transition to the S01 phase through the N'' phase, then the SA phase, and at this time, the phase transition temperature from the N'' phase to the SA phase (hereinafter referred to as the N''-3A point) to the 1 degree higher temperature side of the N''-3A point, an SC° liquid crystal composition in which the pitch of the spiral appearing in the N0 phase is 3 μm or more is more preferable; Particularly preferred is an S01 liquid crystal composition in which the pitch of the helix is 10 μm or more, and the pitch of the helix increases divergently as it approaches the N''-3A point.

Among the optically active compounds of general formula (B), in compounds where the directions of the helices induced in the N'' phase by the chiral groups R1''+R111 on both sides are opposite to each other, the induced helical pitch is quite long. When such a compound is used as the main component of a chiral dopant, adjusting the helical pitch is often unnecessary or easy; however, for boat fishing, the helical pitch can be adjusted to a longer length as follows. be able to.

The helical pitch P (μm) that appears in the N0 phase of an S00 liquid crystal composition containing multiple optically active compounds is determined by Ci representing the concentration of each optically active substance and Pi representing the pitch of the helix per unit concentration of each optically active substance.
(μm) (Here, the pitch of the spiral is defined as positive for right-handed spiral and negative for left-handed spiral).
Pl at 5A-N'' point T0 of the liquid crystal composition is p, i
, then choose Ci such that, where Pi
can be measured by adding a unit concentration of each optically active compound to the SC matrix liquid crystal having an N phase.

In reality, To changes depending on each Ci, but it can often be estimated fairly accurately from the concentration of each optically active compound in the SC matrix liquid crystal, and the change in the 5A-N'' point when adding ΣCt, etc. If the estimated value T, 1 and the To of the composition selected using it are significantly different, 70/
Instead, measure again using Tyu.

The temperature range in which the SC* liquid crystal composition of the present invention exhibits the N'' phase is preferably 3 degrees or more and less than 30 degrees.

If the temperature range in which the N" phase is exhibited is less than 3 degrees, it is not preferable because the phase transition to the SA phase occurs immediately when the temperature decreases, making it difficult to sufficiently align liquid crystal molecules in the N" phase. If the temperature range showing the N" phase is 30 degrees or higher, the clearing point of the 30$ liquid crystal composition becomes high, which tends to adversely affect workability in the process of filling the cell with the liquid crystal material, which is not preferable. .

A chiral dopant, when added to an SC host liquid crystal, regardless of whether or not the chiral dopant itself has liquid crystallinity, either (1) tends to expand the temperature range in which it exhibits the N'' phase, or (2) exhibits the N'' phase. Each has its own unique properties, such as those that tend to narrow the temperature range in which they occur. SC of the present invention
*In order to adjust the temperature range in which the liquid crystal composition exhibits the N''' phase to the above-mentioned preferred range, in the case of (1), the SC base liquid crystal exhibits a narrow temperature range in which it exhibits the N phase, or it does not exhibit the N phase. S
A C base liquid crystal may be used, and in the case of (2), an SC base liquid crystal that exhibits an N phase over a wide temperature range may be used. This method can be applied not only to the N1 phase but also to the SA phase and the SC'' phase. For example, the chiral dopant expands only the SA phase of the S01 liquid crystal composition, and the N0 phase and the SC'' phase. In order to reduce the size of the SC base liquid crystal, use one that has a high upper limit temperature for the SC phase, a wide temperature range for the N phase, and has a phase sequence of SC phase→N phase→■ phase, or one that has the SA phase. It is sufficient to use a material having a narrow temperature range<SC phase→SA phase→N phase→I phase.

This tendency of chiral dopants can be easily determined by measuring the change in phase transition temperature of an SC liquid crystal composition obtained by adding a certain amount of chiral dopant to an SC base liquid crystal. Therefore, the temperature range in which each phase in the sc'' liquid crystal composition exhibits the N'' phase can be easily adjusted.

The chiral dopant used in the present invention is required to induce a certain level of spontaneous polarization (hereinafter abbreviated as P) by adding it to a certain amount of SC host liquid crystal.

As described above, in the SC0 liquid crystal composition, the amount of chiral dopant to be added may be adjusted so that the value of P is in the range of 3 to 30 nC/cm2, especially near room temperature. However, when the value of P induced by the chiral dopant is small, the amount added is large relative to the SC base liquid crystal, and the viscosity of the S01 liquid crystal composition increases accordingly, resulting in a high-speed response. This is not preferable because it tends to make it difficult to obtain the desired characteristics. Therefore, the chiral dopant used in the present invention is preferably one that can induce P of 1°O+IC/C1l'' or more when added to the SC base liquid crystal by weight%, and 0.0% when added to the SC base liquid crystal at 5% by weight. 5
Particularly preferred is one that can induce P of nC/cm'' or more.

[Examples] The present invention will be specifically explained below with reference to Examples, but the gist and scope of the present invention are not limited by these Examples. In addition, in the examples, "%" represents weight %. The phase transition temperature of the composition can also be measured using a polarizing microscope equipped with a temperature control stage and a differential scanning calorimeter (D
SC) was used in combination.

Example I When added to the SC base liquid crystal to form an SC'' liquid crystal composition, 45% of the compound of the formula is mixed with 45% of the compound of the formula to make it appear in the NI phase as a compound that causes a right-handed helix to appear in the N1 phase. Chiral dopants with controlled helical pitch were prepared.

The spontaneous polarization value of the S00 liquid crystal composition obtained by adding 10% of this chiral dopant to the Sc host liquid crystal shown below at 25°C was 15 nC/cm''.

The SC matrix liquid crystal used has the above general formula (1-a-1)
A composition (hereinafter referred to as base liquid crystal (A)) consisting of 55% of the compound represented by the formula and 35% of the compound that causes the appearance of a left-handed helix, has an SC phase at 57°C or less. showed an SA phase at temperatures below 64.5°C, and an N phase at temperatures below 69°C. In addition, 60°C
The value of the helical pitch in is an extrapolated value.

Next, as a medium temperature range liquid crystal, an SC base liquid crystal consisting of 25% of the compound, 25% of the compound, and 25% of the compound, was prepared from the compound represented by the general formula (I-b-1). (Hereinafter, the mother liquid crystal (
B). ) Next, 16% of the above chiral dopant, 3 base liquid crystals (A)
6% of the parent liquid crystal (B), and 12% of the compound of the formula (u-28) as the thinning liquid crystal.

This SC* liquid crystal composition exhibits an SC'' phase at temperatures below 51.5°C, an SA phase at temperatures below 53.5'C, and an N1 phase at temperatures below 56.0'C. Oriental liquid (
1) It became a phase. Furthermore, it did not crystallize even when left at room temperature or below for a long time, and its melting point was not clear.

This SC''' liquid crystal composition was filled into a cell with a thickness of approximately 2 μm consisting of two glass transparent electrodes that had been subjected to alignment treatment (polyimide coating/rubbing treatment), and was slowly cooled from the ■ phase to room temperature. , showing extremely good orientation,
Uniform monodomains were obtained.

This cell has an electric field strength of 10 V P-P/um, 50
When a Hz rectangular wave was applied and the electro-optical response speed was measured, a high-speed response of 47 μsec at 25° C. was confirmed.

The tilt angle at this time is 20'', and the spontaneous polarization is 29nC/c.
mz, and the contrast was good.

Example 2 In Example 1, the formula (II-2
An SC'' liquid crystal composition was prepared in the same manner as in Example 1, except that the same amount of the compound of formula (II-43) was used in place of the compound of 8).

This SC'' liquid crystal composition exhibited an S01 phase at 47°C or lower, an SA phase at 5BiC or lower, and an N1 phase at 60°C or lower.

The electro-optical response speed measured in the same manner as in Example 1 was 52 μsec at 25°C.

[Effects of the Invention] The ferroelectric liquid crystal composition of the present invention is a liquid crystal material that has excellent orientation and high-speed response, and can operate in a wide temperature range including room temperature.

Therefore, the ferroelectric liquid crystal composition of the present invention is extremely useful as a material for liquid crystal devices using ferroelectric smectic liquid crystals.

Claims (1)

[Claims] 1. Contains medium temperature range liquid crystal and reduced viscosity liquid crystal, smectic C
A ferroelectric liquid crystal composition prepared by adding a chiral dopant to a liquid crystal composition exhibiting a phase, wherein the viscosity-reducing liquid crystal has a general formula (A
) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R^a and R^b each independently represent the number of carbon atoms of 1
~18 linear or branched alkyl group, R
At least one of ^a and R^b has 1 carbon atom
~18 straight chain alkyl group. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ is ▲mathematical formulas, chemical formulas,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or ▲There are mathematical formulas, chemical formulas, tables, etc.▼, and ▲There are mathematical formulas, chemical formulas, tables, etc.▼ represents a trans-1,4-cyclohexylene group. ) A ferroelectric liquid crystal composition exhibiting a chiral smectic C phase over a wide temperature range including room temperature. 2. R^a and R^b are each independently a linear alkyl group, and ▲ has a mathematical formula, chemical formula, table, etc. ▼ is a ▲ mathematical formula,
The ferroelectric liquid crystal composition according to claim 1, which has chemical formulas, tables, etc. ▼ or ▲ has mathematical formulas, chemical formulas, tables, etc. ▼. 3. The chiral dopant has the general formula (B) Q^1^*-Z-Q^2^* [In the formula, Q^1^* and Q^2^* are different optically active groups, and each The optically active group has at least one asymmetric carbon atom, and in at least one of Q^1* and Q^2^*, the asymmetric carbon atom is oxygen, sulfur, nitrogen, fluorine, It has a structure directly connected to chlorine or ▲There are mathematical formulas, chemical formulas, tables, etc.▼ or -C≡N. Z is a general formula (C) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲Mathematical formulas,
There are chemical formulas, tables, etc. ▼ and ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ are each independently ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ Mathematical formulas, chemical formulas,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼, ▲ Mathematical formulas, chemical formulas,
There are tables, etc. ▼, ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼
or represents a structure in which any one or two hydrogen atoms on these rings are substituted with a fluorine atom or a cyano group, and Y^1 and Y^2 each independently represent a single bond, -COO-, -OCO- , -CH_
2O-, -OCH_2-, -CH_2CH_2-, -C
≡C-, -COS- or -SCO-, and m represents 0 or 1. ) represents the central skeleton (core) part of a liquid crystal molecule. ] Claim 1 or 2 containing an optically active compound represented by
The ferroelectric liquid crystal composition described above.